Impact of ultrasonication on the physicochemical, structural, thermal and functional properties of Mung bean protein

Mung bean protein has shown limited use in food industry due to its low foaming, emulsifying, swelling, water and oil-holding activity. Therefore, in this study ultrasonication as a green technology was used to investigate its impact on all these functional properties of Mung bean protein with an aim of increasing its utility in food industries. Protein from Mung beans were extracted using iso electric precipitation method and then nano-reduced using ultrasonication. Dynamic light scattering (DLS) was used for determining the average particle size and polydispersity index (PDI) of native (NP) and ultrasonicated mung bean protein (USP). The average particle size was found to be 10.37 m and 484 nm respectively with PDI value of 0.32 and 0.26. The Ultra performance liquid chromatography (UPLC) profile showed an increase in the essential amino acids of USP (Aspartic acid, leucine, lysine) which might be due to the exposure of hydrophobic amino groups during sonication. Further, the ultrasonicated protein showed a significant increase in functional properties except for water holding capacity which was found to decrease from 3.71 g/g to 2.1 g/g. The radical scavenging activity as measured by DPPH and ABTS assays showed a significant increase in USP with DPPH activity rising from 36.77 to 52.38 % and ABTS activity increasing from 44.57 to 66.71 %. Scanning electron microscopy (SEM) showed topographical changes in the microstructure of protein after nano-reduction confirming that ultrasonication altered the secondary structure of NP. The alteration in the functional groups and conformational attributes were also evaluated using Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Differential scanning calorimetry (DSC) revealed that the denaturation temperature (11.23 degrees C) and enthalpy (0.19 J/g) of ultrasonicated protein was significantly reduced. From this study it was concluded that ultrasound can successfully produce protein nanoparticles with enhanced structural, functional and thermal characteristics making them suitable for use as functional food ingredients.